Not sure if it is a tagging issue, especially since I don't know how the tags are integrated. For example the vanilla swords don't even have a weapons tag, but they still work tagged as a sword. Meanwhile the polearms from other mods are simply 'weapons', like the one in the image, and work fine with affixes.

Out of curiosity, which mod shows you that information. I think I need it in my dev environment ...

So I went in depth this time. We'll need to make a complete datapack for it.

I will get on that and maybe have a chat with the apotheosis dev to see if he can help us forward with it.

We have a preliminary datapack available on our discord. We will be expanding on this, now that our 4 piece armor sets are released.
Expect it to become core to the mod in the near future.